1. Field of the Invention
The present invention relates to a sheet original feeding apparatus mountable on an overhead projector (OHP) on which a sheet original comprising an elongated transparent sheet having thereon information such as an image, a graph or the like are rested and which is adapted to project such information on a screen, and more particularly, it relates to a sheet original feeding apparatus wherein a plurality of sheet originals are stocked and the sheet originals are effectively fed to a projecting station successively.
2. Related Background Art
Conventionally, in a conference or lecture, when the lecturer performs the presentation of the information recorded on OHP films (sheet originals) by using a projector, a plurality of sheet originals on which the information is recorded have previously been prepared in explanation order, and the lecturer himself or a assistant manually rests the originals one by one on a transparent and permeable glass platen of the overhead projector, thereby projecting the information in the original on the screen, and the used original is manually removed and a new original is rested on the platen.
On the other hand, regarding a 35 mm film having images thereon contained in the mount, since the images in the film can be protected by the mount, the exchange of the images in the film has been automatically effected by using an auto carrier device so that the film can mechanically be fed successively. In this case, however, since the small image in each frame of the film must be projected in an enlarged scale, the image quality was worsened, and the dark room was required because of the reduction in the light amount.
By the way, an OHP apparatus can eliminate the above-mentioned drawbacks, can project images on a large-sized film and can present the image information with good image quality in a relatively light room. In an OHP film used with such OHP apparatus, original images can easily be formed on the film by performing the high speed treatment regarding a conventional silver salt film, or by forming digital color images by an electrophotographic method, or by a high image quality ink jet method.
However, in the above-mentioned conventional techniques, the exchanging efficiency of sheet originals in accordance with the progress of the lecturer's presentation has not been improved, since it was difficult to handle the OHP film because of the large size thereof. Accordingly, it has been desired that the original image film was automatically fed to the projecting station on the OHP apparatus.
Incidentally, in order to pick up the high image quality films one by one from the film stack successively and to rest the picked-up film on the glass platen of the OHP apparatus without damaging the surfaces of the films, a method (adopted to a copying machine) wherein sheets are separated one by one by utilizing the friction slip between the sheets in a sheet stacking station such as a sheet feeder cannot be used.
Further, since any original image film among the used and re-stacked original image films may be used again to project it again in the course of the presentation, it is desired to propose a solution having the safety and high reliability and which can easily pick up the film without damaging the film surface.